This invention relates to semi-automatic firearms and especially to a semi-automatic gas-operated shotgun.
The embodiment of the invention which is specifically disclosed herein is a 10-gauge shotgun. However, it must be understood that the invention as defined in the appended claims is also usable in other forms of firearms such as rifles and, naturally, shotguns of other gauges. Therefore, when terminology specific to shotguns is used, the equivalent terminology appropriate for the firearm of interest may be substituted in the disclosure and the claims. For example, the term "shells" as used herein may be replaced with "cartridge" when the invention is to be employed in a rifle.
A shell-feed system in a shotgun or a rifle, in which shells are fed from a magazine onto a shell carrier which then lifts them into position to be chambered by a bolt, should provide a shell feed control mechanism which permits the shells to be fed only one at a time from the magazine to the shell carrier so that the following shell does not jam the shell carrier. This can be done by providing a shell stop which is operated by the shell being fed from the magazine to stop the following shell in the magazine from protruding over, and jamming, the shell carrier.
The shell stop should also permit loading of the magazine from the feeding end by shifting out of its position in order to leave an unimpeded path for the passage of the shells forwardly into the magazine.
In the prior art, this function is accomplished by use of primary and secondary shell stops, or by an intricate assemblage of levers and springs which complicate the mechanism, increasing its costs and decreasing its reliability.
Another problem encountered in firearms of this nature is the problem of latching the shell carrier during the cycle of operation of the firearm in which the shell is to be advanced onto the shell carrier, and to unlatch the shell carrier when the shell is to be lifted to chambering position and also when the firearm is in breech position so that the shells may be loaded into the magazine. In the prior art, a latch is provided which holds the shell carrier in its lowered, shell-receiving position. The latch is necessary to prevent the rearward travel of the slide from causing the shell carrier prematurely to begin rising toward its shell chambering position before the shell has fully loaded onto the carrier. The carrier must remain in its loading position until the shell is clear of the magazine and in correct position on the carrier or the shell will jam the carrier midway in its travel toward chambering position. The latch is usually tripped by the shell when it has fully loaded onto the shell carrier.
The latch also holds the carrier in its loading position when the gun is in the breech position, to prevent the carrier from kicking upward, under the influence of the recoil, into the path of the shell being fed from the magazine. Otherwise, the carrier could be jammed by the feeding shell or fail to receive and load the shell altogether. Although the latch usually performs its function well enough, it does represent an additional part which adds to the expense and reduces the reliability of the gun.
In a semi-automatic firearm, or "auto loader", in which a shell is reloaded and the action is cocked by the discharge of the firearm, it is necessary to provide a mechanism for disabling the trigger so that continued rearward pressure on the trigger does not release the hammer and permit it to ride forward with the bolt on its return stroke, thereby uncocking the gun. All semi-automatic weapons are equipped with a mechanism of this nature, usually called a "trigger disconnect".
The trigger disconnect is usually placed low in the trigger housing where it is nearly inaccessible without disassembling the trigger housing assembly. It should thus be simple and rugged to ensure that it will operate irrespective of neglect and abuse by the owner. Therefore, it should not be dependent on proper cleaning and oiling but it must operate reliably under any condition in which the gun might conceivably operate.
To maximize the reliability of the trigger disconnect structure, it must be formed of simple, rugged parts and be of a design which does not depend for its operation on small tolerances of closely fitting pieces or on fine design shapes which are subject to wear and failure in the presence of dirt or abusive treatment. Moreover, to decrease the cost, the parts should be of simple design amenable to mass production manufacture and simple, fast and trouble-free assembly.
A rifle or a shotgun is often used in the field far removed from a gunsmith or a well equipped shop, and therefore it is desirable that it be possible easily to disassemble the shotgun to its major assemblies to facilitate cleaning and oiling. Therefore, it is desirable that the shotgun be easily disassembled without the use of tools and, when assembled, it must positively be prevented from inadvertant disassembly or loss of parts.
To remove the bolt from the receiver in a shotgun, it is necessary to remove the charging handle. Prior art shotguns employ screws or spring assemblies to hold the charging handle in the receiver, and require the use of tools to remove the charging handle. Even the screws and spring arrangements, however, have not been sufficient to prevent occasional loss of the charging handle during use of the shotgun. These complicated assemblies have thus done little to decrease the chance of loss of the charging handle, but have added to the cost, assembly time and difficulty of field stripping the guns. Therefore, the art has long sought, in vain, for a simple and reliable arrangement for securely holding the charging handle in the bolt and slide.
Another persistent problem in the past has been the ease and frequency with which shotgun shell extractors can become dislodged and lost. An extractor, by its very nature, must be pivotally and removably mounted within the bolt to be able properly to engage the rim of the shell, and to be replaceable when it becomes worn. In the past, the necessity for pivotally mounting the extractor removably in the bolt has also meant that the extractor can, and does, become dislodged and lost. Therefore, it has been a long and heretofore fruitless effort in the art to design an extractor to operate pivotally and yet reliably engages the shell rim and is positively held in place against inadvertently becoming dislodged and lost, while being easily replaceable in the event of breakage or wear.